Showing papers by "University of Queensland published in 1985"

Reproducibility and validity of a semiquantitative food frequency questionnaire

Abstract: The aim of this study was to evaluate the reproducibility and validity of a 61-item semiquantitative food frequency questionnaire used in a large prospective study among women. This form was administered twice to 173 participants at an interval of approximately one year (1980-1981), and four one-week diet records for each subject were collected during that period. Intraclass correlation coefficients for nutrient intakes estimated by the one-week diet records (range = 0.41 for total vitamin A without supplements to 0.79 for vitamin B6 with supplements) were similar to those computed from the questionnaire (range = 0.49 for total vitamin A without supplements to 0.71 for sucrose), indicating that these methods were generally comparable with respect to reproducibility. With the exception of sucrose and total carbohydrate, nutrient intakes from the diet records tended to correlate more strongly with those computed from the questionnaire after adjustment for total caloric intake. Correlation coefficients between the mean calorie-adjusted intakes from the four one-week diet records and those from the questionnaire completed after the diet records ranged from 0.36 for vitamin A without supplements to 0.75 for vitamin C with supplements. Overall, 48% of subjects in the lowest quintile of calorie-adjusted intake computed from the diet records were also in the lowest questionnaire quintile, and 74% were in the lowest one of two questionnaire quintiles. Similarly, 49% of those in the highest diet record quintile were also in the highest questionnaire quintile, and 77% were in the highest one or two questionnaire quintiles. These data indicate that a simple self-administered dietary questionnaire can provide useful information about individual nutrient intakes over a one-year period.

Glacial geology and glaciology of the last mid-latitude ice sheets

Abstract: Satellite imagery and data from ground surveys are used to reconstruct the integrated pattern of the principal longitudinal and transverse features produced on a continent-wide scale by the last ice sheets in Europe and North America. From modern analogues, it is argued that most longitudinal features reflect flow in the outer zone of the ice sheet, and that most major transverse features reflect relatively stable ice-sheet margins. These principles are tested and, using them alone, detailed patterns for the decay of the last ice sheets in North America, Europe and the British Isles are produced, and periods during which they attained near steady-states identified. These patterns can be calibrated by dated sequences to yield deglaciation isochrons. Application of glaciological models to these geological reconstructions generates detailed prediction of net ablation for the period of ice-sheet decay and, by using evidence of last glaciation stratigraphy, models of the dynamic behaviour of the ice sheets throughout the last glacial period are constructed. These enable volumetric changes, oceanic isotopic changes and erratic dispersal pathways to be reconstructed. Erratic dispersal patterns give a good indication of the long-term distribution of centres of ice sheet mass. Discrepancies between predicted and empirical oceanic isotopic records indicate ways in which the conventional continental timescale of glacial change must be altered to fit the better-dated deep ocean record. In addition discrepancies between predicted and empirical erratic dispersal patterns suggest that conventional views of ice-sheet behaviour based on high latitude models may be inappropriate to the dynamically more active mid-latitude ice sheets based in large part on deformable sediment beds.

Expertise in debugging computer programs: A process analysis

Abstract: This paper reports the results of an exploratory study that investigated expert and novice debugging processes with the aim of contributing to a general theory of programming expertise. The method used was verbal protocol analysis. Data was collected from 16 programmers employed by the same organization. First, an expert-novice classification of subjects was derived from information based on subjects' problem solving processes: the criterion of expertise was the subjects' ability to chunk effectively the program they were required to debug. Then, significant differences in subjects' approaches to debugging were used to characterize programmers' debugging strategies. Comparisons of these strategies with the expert-novice classification showed programmer expertise based on chunking ability to be strongly related to debugging strategy. The following strategic propositions were identified for further testing. 1. (a) Experts use breadth-first approaches to debugging and, at the same time, adopt a system view of the problem area; (b) Experts are proficient at chunking programs and hence display smooth-flowing approaches to debugging. 2. (a) Novices use breadth-first approaches to debugging but are deficient in their ability to think in system terms; (b) Novices use depth-first approaches to debugging; (c) Novices are less proficient at chunking programs and hence display erratic approaches to debugging.

An isoparametric joint/interface element for finite element analysis

Abstract: A generally applicable and simple joint/interface element for three- and two-dimensional finite element analysis is presented. The proposed element can model joints/interfaces between solid finite elements and shell finite elements. The derivation of the joint element stiffness is presented and algorithms for the treatment of nonlinear joint behaviour discussed. The performance of the element is tested on typical problems involving shell-to-shell and shell-to-solid interfaces.

Relative weight and risk of breast cancer among premenopausal women

Abstract: Although higher relative weight is generally considered to increase the risk of breast cancer, several case-control studies have suggested that the reverse may be true among premenopausal women The association between Quetelet's index (a measure of relative weight calculated as weight/height) and the subsequent incidence of breast cancer was therefore examined during four years of follow-up among a cohort of 121,964 US women who were 30-55 years of age in 1976 In contrast to women who had experienced natural menopause or bilateral oophorectomy, the incidence of breast cancer among premenopausal women decreased with higher levels of relative weight Age-adjusted relative risks for increasing quintiles of Quetelet's index were 100, 090, 090, 073, and 066 (Mantel extension test for trend = -282, p = 0005) This inverse association was not explained by known risk factors for breast cancer and was somewhat stronger when Quetelet's index was computed using reported weight at age 18 years The excess incidence of breast cancer among lean premenopausal women, however, was limited to tumors that were less than 20 cm in diameter, were not associated with metastases to lymph nodes, and were well-differentiated These findings suggest that the apparent excess risk of breast cancer among lean premenopausal women may result at least in part from easier, and thus earlier, diagnosis of less aggressive tumors

Common acquired naevi and the risk of malignant melanoma.

Abstract: The relationship between common acquired naevi and malignant melanoma of the skin was assessed in a case‐control study. In 183 patients and 183 controls matched for sex, age and area of residence, there was a strong association between the presence of pigmented naevi on the arms and melanoma. In comparison with persons having no naevi on the arms, the crude relative risk of melanoma was 28.0 when naevi were present. After adjusting for hair colour, propensity to sunburn and lifetime sun exposure, the final risk estimate was 30. 1. Family history did not appear to be a determinant of disease independent of the above risk factors.

The crystal growth of silicon in Al-Si alloys

Abstract: Some crystallographic observations of primary silicon and unmodified eutectic silicon in aluminium-silicon alloys are summarized and used to support the theory that sodium modification is due to the poisoning of active growth centres. The implications of endogenous growth in unmodified aluminium-silicon sand castings are explored and mechanisms are proposed for the flake-fibre transition in chill-modified and sodium-modified alloys.

Study of two-component system with failure interaction

Abstract: The literature on multicomponent systems, though extensive, has dealt mainly with formulations where the failure of a component has no effect or influence on the operation or failure of other components in the system. In many real-life multicomponent systems, the failure of a component has some effect on one or more of the remaining components. The paper considers a two-component system with a specific type failure interaction and obtains expressions for the expected cost of operating the system for both finite and infinite time.

Antimicrobial activity of tropical and subtropical sponges

Abstract: Extracts of 19 of 24 species of sponge collected from Queensland. Australia, inhibited the growth of test microorganisms in in-vitro assays. A similar result has been obtained by earlier workers for extracts of species of sponge obtained from temperate waters. Some of the extracts, including extracts of Thorecta vasiforis, Arenochalina mirabilis and Acanthella kleutha, showed activity against bacterial strains that was comparable with that exhibited by penicillin G and streptomycin against these strains. Gram-positive bacteria were expecially sensitive to many extracts. Little activity was exhibited by any extract against four species of fungi tested. Some of the extracts were markedly toxic to one or more of the test organisms (a fish, a crustacean and a hydroid) used, but no clear pattern linking toxicity to these organisms with antimicrobial properties of the extracts emerged. In general, there bas a negative correlation between antimicrobial activity and surface-fouling, raising the possibility of using freedom from surface-fouling as an indicator of antimicrobial activity. Four of five encrusting species from the undersides of coral boulders showed antimicrobial activity. This study confirmed the value of using methanol-toluene extracts in field-based screening programmes, but emphasised the need to use additional extracting media such as methylene chloride in order to augment the number of antimicrobial compounds detected. There are indications that antimicrobial activity may be widespread in the order Dictyoceratida, in the order Verongida and in the order Axinellida, but sporadic in other orders of Porifera.

Plant uptake and phytotoxicity of boron in Australian fly ashes

Abstract: French bean (Phaseolus vulgaris cv. Redland Pioneer) and Rhodes grass (Chloris gayana cv. Pioneer) were grown in glasshouse experiments to examine the potential for phytotoxicity of B in a range of Australian fly ashes. In each experiment, the ashes used were either untreated, leached or adjusted to pH 6.5 and subsequently leached. In the first eperiment, the yield and B status of plants grown on five fly ashes mixed (5 and 10% by weight) with an acid-washed sand were measured and, with the exception of one ash, yield differences among ash sources and among ash treatments were attributed to differences in the degree of B toxicity. In a subsequent experiment, a fly ash with properties representative of most Australian ashes was mixed (0, 15, 30, 70 and 100% by weight) with a sandy loam, and the yield and mineral composition of plants grown on these mixtures determined. Although the available water capacity of the soil was substantially increased by fly ash addition, incorporating large proportions of untreated fly ash resulted in poor plant growth primarily due to B toxicity. In both experiments, leaching the ash reduced the potential for B toxicity, whereas adjustment of the pH to 6.5 and subsequent leaching of the fly ash resulted in plants with normal levels of B. There were marked differences in both the tissue levels of B and the extent of B toxicity symptoms between the two species. Rhodes grass appeared to be able to tolerate higher B contents in the growing medium by taking up much less of the element than French bean. The results indicate that phytotoxicity of B would be a major problem in establishing vegetation on ash dams and in the agronomic utilization of unweathered fly ashes in Australia.

The mixture method of clustering applied to three-way data

Abstract: Clustering or classifying individuals into groups such that there is relative homogeneity within the groups and heterogeneity between the groups is a problem which has been considered for many years. Most available clustering techniques are applicable only to a two-way data set, where one of the modes is to be partitioned into groups on the basis of the other mode. Suppose, however, that the data set is three-way. Then what is needed is a multivariate technique which will cluster one of the modes on the basis of both of the other modes simultaneously. It is shown that by appropriate specification of the underlying model, the mixture maximum likelihood approach to clustering can be applied in the context of a three-way table. It is illustrated using a soybean data set which consists of multiattribute measurements on a number of genotypes each grown in several environments. Although the problem is set in the framework of clustering genotypes, the technique is applicable to other types of three-way data sets.

Corrosion of stainless steels in chloride solution: An XPS investigation of passive films

Abstract: Five commercial steels ranging from the martensitic stainless steel containing 12% chromium to the superferrite containing 29% chromium, 4% molybdenum, and 2% nickel have been studied by XPS. In addition, a pure iron-chromium alloy containing 7% chromium has been investigated. Armco iron and pure chromium (99.99%) were included as references. The formation of the passive films (or corrosion) occurred in deoxygenated 0.1 M NaCl solution (pH=5.6), from which the samples were transferred directly to the XPS chamber under controlled atmosphere (Ar). Concentration profiles (at.-%) of the alloy constituents in their oxidized and metallic states have been determined separately from the measured XPS depth profiles. Forc≳= 12% chromium the passive films have the following structure: there is a depletion of Cr in the inner region, followed by an enrichment (concentration maximum) in the central region of the films. The height of this maximum increases, and its position shifts towards the surface with increasing chromium content in the alloy. The outermost monolayers are rich in water and hydroxyl groups. Various significant properties of the films change drastically at the critical chromium concentration of about 12%. This behaviour is rather independent of the other components (Mo, Ni, Cu) present in the alloys and is discussed in terms of a phase transition in the films which is controlled by the chromium concentration.

Rapid Sequential Intravenous Administration of Four Hypothalamic ReleasingHormones as a Combined Anterior Pituitary Function Test in Normal Subjects

Abstract: Normal subjects were studied to test the feasibility of a combined anterior pituitary function test using iv administration of four hypothalamic releasing hormones: ovine corticotropin-releasing hormone, human GH-releasing hormone, GnRH, and TRH. Initially, nine normal men were studied with various combinations of these four hormones to exclude the possibility that they might inhibit or synergize with each other in releasing the individual anterior pituitary hormones. When given in combination, the releasing hormones were administered as sequential 20-sec iv infusions in the following order and doses: ovine corticotropin-releasing hormone, 1 microgram/kg; GnRH, 100 micrograms; human GH-releasing hormone, 1 microgram/kg; and TRH, 200 micrograms. Plasma or serum samples were assayed for ACTH, cortisol, GH, PRL, FSH, LH, and TSH at multiple times for 120 min after injection. Compared to individual administration, combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the individual hormone responses of these normal subjects. Side-effects of the combined test were the same as those observed with individual hormone administration. No unusual or dangerous side-effects were observed. Having confirmed the efficacy of combined administration of the four releasing hormones, we administered the combination to five additional normal men and 12 normal women. Anterior pituitary hormone and cortisol responses were the same in men and women, except for a lower LH and a greater PRL response in women. There was a rapid increase in all hormones, with peak levels usually reached by 60 min. Adequate assessment of individual hormone responses can be achieved by assaying a basal and only 2 (or 3 in the case of ACTH and GH) postinfusion samples. A rapid, safe, and useful test of combined anterior pituitary function appears to be feasible using these four hypothalamic releasing hormones.

Hormonal factors and melanoma in women.

Abstract: The effect of exogenous hormones and reproductive factors on the risk of melanoma in women was investigated in a case-control study. Data from 91 women, aged from 15 to 81 years, and 91 matched controls were analysed in relation to use of oral contraceptives (OC), parity, age at the birth of the first child, and calculated length of ovulatory life. When potential confounding factors (including pigmentary characteristics and the lifetime exposure to sunlight were taken into account, there was no increase in risk of melanoma in relation to OC use, parity, or age at the birth of the first child. An unexplained association between melanoma and ovulatory life of greater length than 20 years was observed. The general findings of this study suggest that neither hormonal nor reproductive factors increase the risk of melanoma in women.

The need for a taphonomic perspective in stone artefact analysis

Abstract: In Australia a number of taphonomic studies suggest that natural processes may cause stone artefacts to move vertically within a site (Stockton 1973, Hughes and Lampert 1977, Stern 1980), and to move around the landscape (Cane 1982). There seems to be a consensus amongst Australian archaeologists that, while stone artefacts may be moved vertically or horizontally, they are virtually indestructible. Consequently it is believed that interpreting artefact numbers and morphologies requires no taphonomic perspective at all.

The marriage alliance in the roman elite

Abstract: Elite marriage in Rome in the late Republic and early Empire was contracted between noble houses of equivalent status, often for immediate political gains. Contrary to views advanced by some scholars, spouses nonetheless entertained strong expectations of conjugal loyalty and happiness but marriage was relatively fragile. Power was vested in the older generation rather than men as such. A separate matrimonial regime was usually maintained during marriage and dowry was essentially recoverable on divorce or widowhood. Upper class women were therefore relatively independent although they subordinated individual preference to corporate interests. Their primary loyalty was to their natalkin but they observed the obligation to redistribute their dowry and patrimony in the following generation to their children, who belonged to the father's lineage.